Arcam Alpha 7 CD Repair


Arcam Alpa 7 CD Repair

A friend asked me to take a look at an Arcam Alpha 7 CD player that had a loading problem - the drawer opened and closed but, once closed with a CD present, the CD would not load correctly. As it turned out, this wasn't the only problem the player had, but that will come later...

The unit is relatively simple to open and the internal layout is quite uncluttered:

Arcam 7 CD Internal View

In order to investigate the loading problem, it was necessary to remove the CD loading mechanism - a Sony CDM-14. The mechanism is held in place by one screw at the rear and two plastic rivets (no expense spared for this premium product...).

 With the CD drawer open, the decorative panel on the front can be gently slid off vertically to enable the mechanism to be withdrawn later:

CD decorative drawer front on

CD decorative drawer front off


Free the flexible cable from the ties that anchor it to the top of the CD mechanism and then the mechanism can be accessed by removing the screws and the rivets. The latter can conveniently be popped out by gentle pressure to the pin:

CD Mechanism Foot Fixing

You can remove the top of the unit by gently squeezing the lugs on either side, but it may not be necessary:

CD mechanism top fixing lugs

The mechanism has two motors - one to spin the CD and one to drive the loading mechanism. The loading motor has its own small PCB and is found on the underside of the transport mechanism:

CD Loading Board

You will notice written vertically on the right of the picture "IN SW" and on the left "OUT SW". These are microswitches that detect when the drawer is fully closed and fully open, respectively - they engage with mouldings on the bottom of the CD drawer. They're actually "naked" microswitch blades with a plastic sleeve over them on the other side of the PCB. You can see their position in this fragment of the exploded diagram from the service manual (they're the bits that stick up either side of the motor):

Position of CD microswitches

It transpires that the "IN SW" was bent and not detecting the drawer being closed and it was simply(!) a matter of removing the loading board, removing the clear plastic cover from the microswitch, bending the switch back, replacing the sleeve and reassembling. Take care, however, that the loading board contains a cyclic mechanism to engage the CD clamp and its gears and associated parts will doubtless fall out during its removal and probably again during attempts at reassembly.

This done, a CD could be loaded and the mechanism tracked perfectly. Unfortunately, as soon as the CD player was connected to an amplifier, it became clear that the sound was dreadful. 

This was not an entire surprise - it's common for the electrolytic capacitors in the power supplies of these units to have burst and leaked electrolyte, resulting in an extremely noisy and erratic power supply to the audio circuits. A cursory glance at the PCB revealed the source of the problem:

Leaking electrolytic capacitors

You can clearly see the brown gunge spilling onto the PCB. After replacing the four capacitors (1000µF, 25V) and cleaning up the board, normal service was restored.